Exercise 1 Page 800

(x- h)^2+(y- k)^2= r^2 In this form, ( h, k) is the center of the circle and r is its radius. We are told that the center of the circle is ( 0, 0) and its radius is 4. This is enough information to write the equation. (x- 0)^2+(y- 0)^2= 4^2 ⇕ x^2+y^2=16